Efficient coherent combining of widely tunable fiber lasers

Abstract

We have experimentally demonstrated coherent combining of 2 and then 4 fiber lasers, with respectively 99% and 95% combining efficiency. The combining method investigated here is based on a multi-arm resonator of interferometric configuration. In spite of its interferometric nature, the multi-arm laser operates without significant power fluctuations, even in an unprotected environment. This occurs when the arm length difference is large enough to introduce spectral modulations of period smaller than the laser bandwidth. We have also experimentally shown that the combining method is compatible with wavelength tuning. A Mach- Zehnder Fiber Laser was tuned over a wide spectral range of 60nm. Theoretically then, we confirm that the combining method can be scaled to a large number of lasers without decreasing the combining efficiency.

Coherent addition of orthogonally polarized fibre lasers with high combining efficiency

“…A high combining efficiency can be easily achieved by the method used in this research in contrast to the Michelson coherent locking method. A fundamental limit of the Michelson coherent locking scheme [1] is related to the beam splitter ratio being fixed upon fabrication, and hence any deviation of the power ratio of the two arms from the designed value will result in an effective intra-cavity loss. For example, in case of a 50/50 beam splitter, the combining efficiency can be expressed as…”

“…Due to high radiation intensities inside a fibre, optical breakdown and nonlinearities are limiting the power extractable from a single fibre laser. A convenient approach to coherent addition of fibre lasers is based on the use of a multi-arm resonator in an interferometer configuration [1][2][3][4][5][6][7][8][9][10]. The coherent combining takes place due to self-organization in laser generation that ensures amplification of resonator modes with the lowest losses.…”

“…Michelson and MachZehnder type resonators have been successfully used to reach nearly 100% combining efficiency of two fibre lasers. Coupling was obtained when two amplifying fibres shared a common output mirror located on one port of a standard 50/50 coupler which mixed both optical beams [1][2][3][4][5][6][7][8][9]. When beams of the two input ports of the beam splitter had the correctly fixed relative phase, they interfered constructively at the output port.…”

Fiber laser sensor based on a phase-shifted chirped grating for acoustic sensing of partial discharges

“…If the mandrel is immersed in a fluid, in general the resonance frequency will lower due to the added mass effect, and it will also decrease the amplitude at the peak due to re-radiation of the acoustic energy [14]. The response is expressed as the normalized radial displacement, W 1,0 ()/R, produced by a pressure wave p of the frequency  …”

“…Erbium-doped fiber ring lasers (EDFRLs) have recently attracted great interest due to such promising applications as optical sensors. The EDFRLs have advantages which include high output power, low intensity noise, and compatibility with fiber components [11][12][13][14][15]. Recently, EDFRLs using the phase-shifted linearly chirped FBG (PS-LCFBG) were reported [16].…”